This invention relates to controllers or power transfer devices of the type that include a movable cable or element traveling inside a conduit. More specifically this invention relates to a force coupling transfer device that allows linear or rotational forces to be transferred between an input device and a controlled device.
Control and power transmission technology is important to consumers and industry. These devices are used in a variety of applications from aircraft, automotive, marine, snowmobiles, machine control, and home appliance markets. This technology involves controlling the movement of parts or devices when linear or rotational force is transferred from one end of an elongated element to the other end. For example, this technology is generally directed to transfer forces from an input device, such as a lever or control pedal, to a controlled device, such as a motor controller, brake, clutch, or accelerator.
Control devices of this type generally have an elongated guide conduit and an elongated core element such as a cable made from woven metal strands, or a solid wire that moves inside of the guide conduit. These control devices may be susceptible to premature wear between the movable core element and the interior surface of the guide conduit because of ineffective lubrication. Further, lubricating an inner movable core element while inside the guide conduit can be difficult or impossible as the guide conduit surface construction that does not usually allow lubricating materials to pass therethrough. Coatings such as tetrafluoro polyethylene (Telfon) have been used as an inner tube liner to minimize the effects of friction and wear. However, this solution may be undesirable in some applications because it can be expensive and deteriorates over time.
In addition, some movable core elements, especially cables, tend to kink inside the guide conduit in response to inadvertent flexing. Kinking is undesirable for dependable operations and can lead to improper force transfer from the input device to the controlled device, and premature concentrated stress failure at the kink.
Thus with a woven cable, the inner cable begins to fail with the break of one strand at a kink. If a solid core is used, it begins to fail as a concentrated stress cracks the outer surface and it works its way through the cable for complete failure. Thus, even a seemingly minor kink or crack with the prior art can result in total failure.
Additionally, a shock load on a woven or solid core cable can also start, propagate, or complete failure because the cable has no ability to give without losing strength to withstand the load.
Still other force transfer devices in the art do not allow convenient, flexible routing through a control space, thus increasing cost to design additional parts. Existing devices also have additional drawbacks in power transmission because some installations of such controls require the conduit and movable core element to be bent in sharp angles which can cause excessive binding and kinking of the inner core element. Thus, a force transfer device minimizing and overcoming these and other drawbacks was needed.
In view of the foregoing, the present invention is directed to an improved force coupling transfer device for transferring linear and/or rotational forces that overcomes the aforementioned drawbacks in the conventional control technology.
An object of the invention is to substantially eliminate the kinking associated with existing technology. Kinking is reduced by utilizing an elongated flexible inner coiled spring positioned inside of an elongated flexible outer sheath that is supported at each end.
Yet another object of the invention is to substantially reduce a portion of the operational cost associated with mechanical actuator control devices in a machinery control environment. Due to the present invention, the elongated flexible outer sheath has the ability to allow lubricating liquids to pass through the outer surface to lubricate the inner coiled spring. This reduces wear between the inner coiled spring and the outer sheath. This advantage can save replacement and maintenance costs associated with labor, materials, and machinery equipment downtime.
These and other objects are achieved by the present invention, which according to one aspect, provides a force coupling transfer device for transferring a force that includes an elongated flexible outer sheath that has a center axis, and an elongated flexible inner coiled spring positioned inside of the outer sheath for movement. The inner coiled spring has an opposing first and second ends and transfers a force applied to the first end to the second end. The inner coiled spring also has a center axis. The outer sheath is permeable along its length to permit lubrication of the inner coiled spring.
In addition, the inner coiled spring sheath reduces the initial shock load from a force in either a pull or rotational operation which will reduce the failure potential of a rigid inner connector. The inner coiled spring activates the controlled equipment in a push or pull operation. Initial shock load on the coiled spring in the pull mode is relieved by a slight elongation of the inner coiled spring at the beginning of pull actuation.
Another object of the invention is to reduce the strain on the elongated flexible outer sheath. One aspect of the present invention provides at least one strain relief device disposed around the outer sheath. The strain relief device reduces strain on the ends of the outer sheath where the outer sheath is most likely to be damaged.
Another object of the invention is to control the operation of a device at a remote location to allow a human operator to perform multiple tasks in a manufacturing environment. This aspect to the invention provides for a force transfer system for use in machinery or equipment that has an input device, a controlled device, an elongated flexible outer conduit having opposing ends and an elongated flexible inner spring disposed inside of the outer conduit for movement. The inner spring also has first and second ends. The input device connects to the first end and the controlled device connects to the second end of the spring. The inner spring provides a force to the controlled device in response to force at the input device.
These and other objects and features of the invention will be apparent upon consideration of the following detailed description thereof, presented in connection with the following drawings in which like reference numerals identify the elements throughout.